It was almost 7 p.m. on Friday, not yet dark, when the couple made their way around the southwest corner of a Washington Heights park. Moments later, they were gone, seemingly swept up from the street, forcibly, by at least two captors.

After two days of scouring the streets and examining surveillance footage for evidence and clues, the police now believe that the bizarre abduction may well turn out to have been a hoax.

Detectives are investigating the possibility that the kidnapping “may have been a hoax staged among friends to celebrate one of their birthdays,” said Paul J. Browne, the Police Department’s chief spokesman.

Police officials had initially said they believed that the couple was abducted at gunpoint and forced into a dark minivan. No one had reported the couple, whom the police have not identified, missing, Mr. Browne said.

The police released two surveillance videos that captured some of the moments before and after the couple’s disappearance. In the videos, the man, who is wearing dark clothing and a hooded sweatshirt pulled up around his head, and the woman, dressed in a three-quarter-length white or light tan coat, walk down West 173rd Street and turn north onto Haven Avenue.

Two men, including one who appears to be shielding his face, are then seen running in the couple’s direction. The minivan appears to follow the two; the driver turns right onto Haven Avenue, driving the wrong direction on the one-way street, with a side door ominously ajar.

On Sunday afternoon, as children dressed for Easter climbed on the jutting bedrock and residents let their dogs run in an enclosed space inside J. Hood Wright Park, the mystery lingered — and theories abounded.

Some speculated that the episode was drug-related, noting that the woman was carrying two bags and a witness reported that she looked over her shoulder, in a nervous manner, just before the minivan zoomed up alongside the couple. One resident wondered if the abduction was part of a kidnapping plot for ransom money; another, half-jokingly, said that perhaps the couple were wanted by the government, and federal agents had whisked them away for questioning.

“It looked like they were targeted,” a resident, Sarah Jacobson, said. “I don’t think it was random.”

If it was a hoax, the question remained: Why would anyone go through the trouble to stage such an elaborate and disturbing ruse?

Witnesses reported hearing the woman scream as two men forced the couple into the minivan at gunpoint, the police said.

Through eyewitnesses, investigators were able to establish a partial license plate number. “There were 16 vehicles of interest, but they all checked out,” Mr. Browne said Sunday.

Detectives went door to door on Saturday, asking residents if they recognized the couple, according to two residents, Luz Riveros and Luis Velez.

Ms. Riveros, 49, said the detectives showed her a photograph that she believed was taken from the surveillance video. “The police asked me if I know the lady in the picture — also if I know the clothes, the coat, she is wearing,” she said. The picture, however, was too grainy, she said.

A version of this article appears in print on , Section A, Page 13 of the New York edition with the headline: Abduction, or Hoax? A Mystery in Manhattan Grows. Order Reprints | Today’s Paper | Subscribe